Earlier results had demonstrated a lasting depletion of hippocampal dynorphin after ischemia in the gerbil. Immunoreactivity in hippocampal extracts remained at 50% of control levels for at least one week after a single 5 min ischemic episode. Immunocytochemical studies verify the localization of dynorphin peptides in hippocampal dentate granule cells an their mossy fiber projections to CA3. The pattern of immunoreactivity remains unchanged during recirculation after transient ischemia, suggesting that the postischemic depletion of dynorphin peptides is homogeneous throughout this cell population. Future studies will evaluate the levels and distribution of prodynorphin mRNA in hippocampus after ischemia.